LONDON — Britain raised its terror threat alert to the second-highest level Friday, one of several recent moves the country has made to increase vigilance against international terrorists after a Christmas Day bombing attempt on a Europe-U.S. flight.

The threat level was raised from "substantial" - where it had stood since July, indicating a strong possibility of a terrorist attack - to "severe," meaning such an attack is considered highly likely.

In making the announcement, Home Secretary Alan Johnson said the raised security level means that Britain is heightening its vigilance. But he stressed that there was no intelligence suggesting...

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He said the decision to raise the threat level was made by the U.K.'s Joint Terrorism Analysis Center. He said the centre kept the security threat level under constant review and made its judgments based on a range of factors, including the "intent and capabilities of international terrorist groups in the U.K. and overseas."

Friday's changes came days after Britain suspended direct flights to Yemen's capital in response to the growing threat from al-Qaida-affiliated militants based in that country. Prime Minister Gordon Brown said his government also was creating a new terrorist no-fly list, and targeting specific airline passengers for tougher security checks.